1. Field of the Invention
The present invention is in the fields of solid-state physics, semiconductor material and heteroepitaxy, and more particularly concerns lattice-matching methods for rhombohedral growth of crystals comprised of semiconductor alloys of group IV and other cubic crystalline materials on the basal plane of trigonal or hexagonal crystalline substrates, and the resulting semiconductor compositions.
2. Description of the Related Art
The alloys of group IV elements, including carbon (C), silicon (Si), germanium (Ge), and tin (Sn) are important semiconductor materials. For example, SiGe alloy is widely used in Hetero Bipolar Transistors (HBT) and High Electron Mobility Transistors (HEMT) for high speed computing and wireless communications, as well as in Thermoelectric (TE) materials. The growth of these alloys has been very difficult because the alloy has a different lattice constant from that of the commonly used substrate, such as Si wafer. Prior efforts have tried to match the lattice constant of cubic structures directly, such as by the approach wherein Ltarget=Lsubstrate (the lattice constant of cubic substrate). However, even a small mismatch of these parameters can result in extremely high pressures in the alloy layer. Thus, in prior efforts, the thickness of the grown layers was very small and often had a high density of defects such as misfit dislocations.
Similar considerations apply with respect to other cubic crystalline semiconductor materials, including group III-V and II-VI materials in zinc-blende structure, as well as other materials in Body Centered Cubic (BCC) and Face Centered Cubic (FCC) structures.